Those skilled in the art are familiar with safety strips such as those disclosed in EP 0 103 726, comprising flexible tubing and the contact elements surrounded thereby. In such devices, the axial prestress ensures that the contact elements make continuous contact with each other in the quiescent condition, is created by tubing which surrounds the contact elements. In addition, the contact elements are interconnected to the tubing by some force or material.
The load on the tubing between the contact elements in such arrangements presents a problem. Longitudinal fluctuations caused by temperature changes, as well as the action of the safety strip produce considerable local stress variations.
Furthermore, although high axial prestressing effects contact between the individual switching elements and thus is desirable, this inevitably results in a lessening of the safety strip's switching sensitivity since the required bending force to stop movement likewise increases.
An additional problem consists in the variations in the prestress since the E-module of the tubing changes depending on temperature and aging.
The object of the invention therefore is the development of a substantively maintenance-free safety strip providing improved switching safety and a longer service life.